A plasma etching is known as one kind of a plasma processing performed upon a processing target object by using a plasma processing apparatus. A resist mask used in the plasma etching is formed by a photolithography technique, and a limit size of a pattern formed on an etching target layer depends on a resolution of the resist mask formed by the photolithography technique. However, there is a limit in the resolution of the resist mask. As a demand for high integration of electronic devices is getting higher, it is required to form the pattern having a size smaller than the resolution limit of the resist mask. By way of example, techniques regarding etching upon a processing target object made of SiC (silicon carbide) are described in Patent Documents 1 and 2 and Non-Patent Document 1. Patent Document 1 discloses an etching method of performing reactive ion beam etching upon SiC by using a mixed gas of CCl2F2 and Ar. Patent Document 2 describes a method of etching SiC by using a gas containing a SF6 gas. Further, Non-patent Document 1 discloses a technique of etching SiC by using a mixed gas containing a CF4 gas, a SF6 gas and a N2 gas.    Patent Document 1: Japanese Patent Laid-open Publication No. H07-193044    Patent Document 2: Japanese Patent Laid-open Publication No. H11-072606    Non-patent Document 1: “Reactive Ion Etching of 6H-SiC in SF6/O2 and CF4/O2 with N2 Additive for Device Fabrication,” R. Wolf and R. Helbig, J. Electrochem. Soc., Vol. 143, No. 3, March 1996